SYRINGES

Abstract: A syringe has a drug-containing cartridge (7) with a bung (8) at one end which is engaged by a plunger (4), and a membrane (9) at its other end which is penetrated by a needle. A connecting structure (11) is connected to (or is formed integrally with) the needle (17) and fits onto the forward end of the cartridge (7) and the syringe. After use the cartridge (7), the connecting structure (11) and the needle (17) can be disposed together. A sleeve (19) is slidably mounted on the structure (11) and can be moved to sheath the needle (17).

Description: SYRINGES This invention relates to syringes. A conventional syringe, e.g. as used by a dentist to administer anaesthetic, has a barrel with a plunger mechanism at one end and a threaded connector for a needle at the opposite end. A drug-containing glass cartridge is inserted into the barrel, the needle is screwed onto the connector so that it penetrates a seal at the forward end of the cartridge, and the plunger mechanism is operated to engage a bung at the rearward end of the cartridge and thereby expel the drug through the needle. After use, the needle and cartridge are removed and discarded. In order to minimise contamination problems, European Application EP 0394295-A describes a syringe in which, in place of the above mentioned cartridge, there is a drug-containing housing which is attached directly to the needle at one end and to the plunger mechanism at the other end. After use the entire housing, including the needle, is detached from the plunger mechanism and discarded thereby avoiding the need to sterilise the barrel and needle connector of the conventional syringe. Whilst this arrangement provides an effective solution to contamination problems, it is necessary for the specially-constructed detachable housing to be pre-filled with the drug which can be inconvenient from a manufacturing point of view. An object of the present invention is to provide a disposable syringe housing which is convenient to manufacture. According to one aspect of the invention therefore there is provided a detachable housing for a syringe comprising a drug-containing cartridge having a bung at one end and a penetrable member at the other end, the cartridge being adapted for connection to a needle at the said other end, such that the needle penetrates the penetrable member, and being adapted for connection to a plunger mechanism at the said one end, so that the bung can be moved down the cartridge to expel the drug through the needle, characterised in that the cartridge is provided with at least one separate structure attachable relative thereto, said structure being adapted for the said connection of the cartridge to the needle and providing means for releasable connection to the plunger mechanism, whereby the housing comprising the cartridge, the (or each) said structure, and the needle can be detached from the plunger mechanism for disposal together. With this arrangement the advantages of disposability can be attained with an arrangement which is particularly simple and convenient to manufacture in so far as it involves the use of a simple drug-containing cartridge which may be of the kind used with conventional syringes. Most preferably there is one said structure which is attachable to the said other end of the cartridge and which is adapted for connection to the needle and which provides the means for connection to the plunger mechanism. Thus, and in accordance with a second aspect of the present invention there is provided a structure for attachment to a drug-containing cartridge of a syringe, which cartridge has a bung at a rearward end and a penetrable membrane at a forward end, said structure being adapted for attachment to a needle and having means for attachment relative to the forward end of the cartridge, and means for attachment to a plunger mechanism. The means for attachment to the cartridge may comprise a clip or constriction or the like which fits around a neck at the forward end of the cartridge, such neck being a feature of conventional cartridges. The structure may be formed integrally with the needle or alternatively it may incorporate means for connection to the needle which may comprise a threaded boss or nipple. The means for attachment to the plunger mechanism may comprise an outer peripheral retaining structure, such as a screw-thread, adapted to mate with a corresponding retaining structure at the end of a barrel extension on the plunger mechanism, which extension fits around the cartridge from the rearward to the forward end thereof. The barrel extension may have a longitudinally movable sleeve which can be moved forwardly to sheath the needle after use. This sleeve may be removable and disposable with the housing. If desired, provision may be made for aspiration, or slight suck back with the syringe so that it can be seen if a vein or atery has been penetrated, such penetration being revealed by suck back of blood. Thus, the said structure may be provided with a spring arrangement which acts to urge the cartridge in a direction away from the needle, in conjunction with a releasable retention device bearing on the top rim of the cartridge. The spring arrangement may comprise a projection engageable with the resilient penetrable member of the cartridge, or an interposed spring means. The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 is an axial section of a syringe provided with one form of a disposable housing in accordance with the invention; and Figs. 2 & 3 are enlarged axial sections of a bottom part of the arrangement of Fig. 1 showing alternative embodiments thereof. Referring to Fig. 1 , the syringe comprises a plunger mechanism 1 (e.g. of stainless steel) having a body part 2 with a finger grip 3, a plunger 4 slidable axially through a bore in the body 2, and a barrel extension 5 coaxial with the plunger 4. The barrel extension 5 may comprise a tube, or apertured tube, or tubular framework. At its forward end, the tubular extension 5 has an internal screw- thread 6. A conventional drug-containing cartridge 7 is used with the syringe, such cartridge comprising a glass tube with a bung 8 within one (rearward) end and a foil covered penetrable membrane 9 across the other (forward) end. The glass tube is shaped to provide a circumferential groove 10 defining a neck close to the forward end. A connection structure 1 1 is attached to the forward end of the cartridge 7. This structure 1 1 comprises a plastics body of cup-shaped form with a cylindrical part 12 which is closed at one end and has a central axialiy projecting boss 13 on its outer face. There is a narrow axial bore through the closed end and the boss 13. The boss 13 and the cylindrical part 12 both have external screw-threads 14, 15. The cylindrical part 12 has an open end bounded by an inturned lip 16. There is sufficient resilience in the lip 16 and/or the associated body of the connection structure 1 1 to enable the structure to be pushed over the forward end of the cartridge 7 so that the lip 16 springs into, or snap fits with, the groove 10 thereby to retain the structure 1 1 securely on the end of the cartridge 7. With the connection structure 1 1 in position the cartridge 7 can be inserted into the barrel extension 5 and held securely in position by screwing the thread 15 of the cylindrical part 12 into engagement with the screw thread 6 at the end of the barrel extension 5. A conventional needle 17 can then be screwed on to the boss 13 so that its rear end penetrates the membrane 9. In this position the rearward end of the cartridge 7 is at the rearward end of the barrel extension 5 and the bung 8 is close to the end of the plunger 4. The syringe can now be operated in the usual way to cause the bung 8 to be displaced down the cartridge 7 with the plunger 4 to expel drug through the needle 17. After use, the connection structure 1 1 is unscrewed from the barrel extension 5 so that the cartridge 7, connection structure 1 1 , and needle 17 can be removed and disposed together. It will be seen that the cylindrical part 12 of the connection structure 1 1 has a lower, or forward portion 18 which is not threaded and which remains outside the barrel extension 5 to provide a convenient finger grip for screwing and unscrewing the structure 1 1. This portion 18 may be enlarged or shaped as desired to further facilitate gripping. As shown in Fig. 1 a tubular sleeve 19 may be engaged around the connection structure 1 1 , such sleeve 19 being movable axialiy between a rearward limit position (as shown) at which it overlies the barrel extension 5 and fully exposes the needle 17, and a forward limit position at which it covers the needle 17. The sleeve 19 is removed and disposed together with cartridge 7 and needle 17 with the sleeve 19 covering the needle 17 to avoid needle stick injuries. The sleeve 19 has inwardly directed recesses 20 at each end which snap fit with projections 21 on the structure 1 1 to hold the sleeve 19 in each limit position. Also, the sleeve 19 may be internally longitudinally grooved to accommodate the projections 21 whereby the sleeve 19 is free to move axialiy but cannot rotate relative to the structure 1 1 . The rotation of the structure 1 1 relative to barrel extension 5 can the. ..fore be effected by rotation of the sleeve 19. With the arrangement described above, full advantages of disposability can be attained using a conventional cartridge. As shown in the modified embodiment of Fig. 2, the structure 1 1 has an upstanding small projection 22 which presses against the penetrable membrane 9 at the end of the cartridge. At the top end of the syringe there is a suitable structure (indicated diagrammatically at 23 in Fig. 1 ) which bears against the top rim of the cartridge and holds the projection 22 pressed firmly into the membrane 9. If this top end bearing structure 23 is now released, and pressure is released from the plunger 4, the cartridge will move slightly upwards due to the resilience of the membrane 9. This gives a very small suck-back or aspiration effect through the needle. This is useful e.g. in dentistry where an injection is being made into soft gum tissue and it is desired to avoid penetration of a vein or artery. If penetration of a vein or artery has occurred the aspiration will cause blood to flow back into the cartridge. Other resilient or spring arrangements may be used to achieve aspiration. Thus, Fig. 3 shows a modification in which the structure 1 1 is formed integrally with the needle 17. Springy transverse projections 24 or fingers are incorporated for resilient engagement with the bottom of the cartridge. It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only. Thus, for example, the embodiment of Fig. 1 utilises a conventional needle and therefore has said connection structure 1 1 which is separate from the needle and is adapted to be interconnected thereto by means of the threaded boss 13. However, if desired, and as shown in Fig. 3, the structure 11 may be formed integrally with the needle so that it is supplied together with the needle. Where the structure 1 1 is interconnected by means of the threaded boss 13 with a conventional needle, the structure 1 1 may be supplied with the needle, or ready fitted on the end of the cartridge or as a separate part to be fitted to the needle and to the cartridge prior to use. The syringe may be as described adapted for end loading of the cartridge. It is however also possible to use a conventional side-loading syringe. The body of the syringe may be formed from plastics or stainless steel or any other suitable material or combination of materials as appropriate. The interconnection between the structure 1 1 and the syringe body need not be through screw threads. Especially in the case of a rigid stainless steel syringe body, the interconnection may be achieved in the manner of a push-in or snap-fit or other clip type connection. Depending on the nature of the syringe and the mode of location of the cartridge therewithin, the structure 1 1 need not clip around or otherwise connect positively to or even engage the end of the cartridge. The cartridge may be held within the body of the syringe in conventional manner e.g. after side loading thereof through the usual side slot or aperture.

Claims: CLAIMS 1. A detachable housing for a syringe comprising a drug-containing cartridge (7) having a bung (8) at one end and a penetrable member (9) at the other end, the cartridge being adapted for connection to a needle (17) at the said other end, such that the needle (17) penetrates the penetrable member (9), and being adapted for connection to a plunger mechanism (1 ) at the said one end, so that the bung (8) can be moved down the cartridge (7) to expel the drug through the needle (17), characterised in that the cartridge (7) is provided with at least one separate structure (1 1 ) attachable relative thereto, said structure (11 ) being adapted for the said connection of the cartridge (7) to the needle (17) and providing means for releasable connection to the plunger mechanism (1 ), whereby the housing comprising the cartridge (7), the (or each) said structure (1 1 ), and the needle (17) can be detached from the plunger mechanism (1 ) for disposal together. 2. A housing according to claim 1 characterised in that there is one said structure (1 1 ) which is attachable to the said other end of the cartridge (7) and which is adapted for connection to the needle (17) and which provides the means for connection to the plunger mechanism (1 ). 3. A structure for attachment to a drug-containing cartridge of a syringe, which cartridge (7) has a bung (8) at a rearward end and a penetrable membrane (9) at a forward end, said structure (1 1 ) being adapted for attachment to a needle (17) and having means (16) for attachment relative to the forward end of the cartridge, and means (15) for attachment to a plunger mechanism (1 ). 4. A structure according to claim 3 characterised in that the means ( 16) for attachment to the forward end of the cartridge comprises means arranged to fit around a neck at the forward end of the cartridge. 5. A structure according to claim 3 or 4 characterised in that said structure (11 ) is formed integrally with the needle (17). 6. A structure according to claim 3 or 4 characterised in that said structure (1 1 ) is formed separately from the needle and incorporates means (13) for connection thereto. 7. A structure according to any one of claims 3 to 6 characterised in that the means (15) for attachment to the plunger mechanism (1 ) comprises an outer peripheral retaining structure adapted to mate with a corresponding retaining structure at the end of a barrel extension (5) on the plunger mechanism (1 ). 8. A structure according to any one of claims 3 to 7 characterised by the provision of a sleeve (19) which is mounted on the structure (1 1 ) for longitudinal movement forwardly to sheath the needle (17) after use. 9. A structure according to any one of claims 3 to 8 characterised by the provision of a spring arrangement (22 or 24) on the structure (1 1 ) which acts to urge the cartridge in a direction away from the needle (17), a releasable retention device (23) being provided to bear on the top rim of the cartridge to resist said urging of the spring arrangement. 10. A housing according to claim 1 or 2 when using the structure of any one of claims 3 to 9.

Inventors: HYMANSON VICTOR, HYMANSON, VICTOR
Applicants: HYMANSON VICTOR, SELDOREN LTD, HYMANSON, VICTOR, SELDOREN LIMITED
Application year: 1994
Main classification: A61M5
IPC codes: A61M5